Donald Tusk, left, pictured with Sweden's Prime Minister Stefan Lofven, warns that Britain must do more before the EU will open up trade talks (Jonas Ekstromer /TT via AP)

Britain has been told to come up with more money over the next fortnight if European Union ministers are to support post-Brexit trade talks by the end of the year.

Nearly eight months after Britain triggered the process to leave the EU, talks remain deadlocked over the amount the UK is prepared to pay to settle its accounts with the rest of the trading bloc.

The UK has fallen short of the 60 billion euro sum sought by Brussels with further stumbling blocks over what will happen along the 310-mile border between the UK and EU-member Ireland, and the fate of EU citizens living in Britain.

Donald Tusk, the president of the European Council, said much more progress was needed on the latter two issues before the EU will agree to discuss trade, an issue considered of prime importance by Britain for its future prosperity.

If leaders do not agree to move to the second phase at the summit in Brussels on December 14-15, then it could mean no progress until the next scheduled European Council in March.

Irish prime minister Leo Varadkar said that made clear that Dublin is ready to delay the start of trade talks beyond the start of next year unless the UK offers further concessions on the border.

“It's 18 months since the referendum, it's 10 years since people who wanted a referendum started agitating for one,” he said. “Sometimes it doesn't seem like they have thought all this through."